Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$160.30	3.423%	$165.7871	$165.79	$165.80	$165.80
Purchase #2	$178.89	10.619%	$197.8863	$197.89	$197.90	$197.90
Purchase #3	$65.73	10.477%	$72.6165	$72.62	$72.60	$72.60
Purchase #4	$145.57	10.191%	$160.405	$160.41	$160.40	$160.40
Purchase #5	$108.97	13.738%	$123.9403	$123.94	$123.95	$123.90
Purchase #6	$135.29	4.794%	$141.7758	$141.78	$141.80	$141.80
Purchase #7	$90.48	10.535%	$100.0121	$100.01	$100.00	$100.00
7 purchase totals =	$885.23		$962.4231	$962.44	$962.45	$962.40